#
# MDEV-4029 SELECT on information_schema using a subquery locks up the information_schema table due to incorrect mutexes handling 
#
select variable_name from information_schema.session_status where variable_name =
(select variable_name from information_schema.session_status where variable_name = 'uptime');
select variable_name from information_schema.session_variables where variable_name =
(select variable_name from information_schema.session_variables where variable_name = 'basedir');

#
# information_schema tables inside subqueries, they should not be re-populated
# (i_s.columns needs to scan i_s itself, creating a tmp table for every i_s
# table. if it's re-populated, it'll do that multiple times)
#
create table t1 (a char);
insert t1 values ('a'),('t'),('z');
flush status;
select a, exists (select 1 from information_schema.columns where table_schema=concat('tes',a)) from t1;
# fix the result in ps-protocol
--replace_result 44 43
show status like 'created_tmp_tables';
drop table t1;